If something goes wrong when InnoDB attempts to
initialize its tablespace or its log files, delete all files
created by InnoDB. This means all
ibdata files and all
ib_logfile files. In case you have already
created some InnoDB tables, delete the
corresponding .frm files for these tables
(and any .ibd files if you are using multiple
tablespaces) from the MySQL database directories as well. Then you
can try the InnoDB database creation again. It
is best to start the MySQL server from a command prompt so that
you see what is happening.